Many of the largest investments Buffett's Berkshire Hathaway has made are in private companies, which investors cannot buy into. For instance, insurer Geico remains one of Buffett's largest and most important holdings. There are no public shares for individual investors to buy.

Buffett, though, maintains a portfolio of meaningful stakes in public companies that can be purchased. This portfolio is widely watched by Buffett followers, because the holdings reveal a glimpse of the companies Buffett sees promise in. Since Buffett holds onto investments for such a long time, investors can also buy and hold along with him.

Buffett disclosed holdings in 15 individual companies in Berkshire's latest annual report. The company Berkshire Hathaway owns the largest percentage of is American Express, with a 13.7% stake worth $8.7 billion. The stake that's worth the most is Wells Fargo, at $15.6 billion.

While Berkshire provides great detail, the company does have some smaller positions that are grouped into an "others" category. The full list is available in the annual report.